The aim of this project is to determine the degree to which reading ability is related to local (detail) and global (wholistic) information processing operations. Early readers (aged 8 - 9 years) will be classified through the use of individually administered reading tests as good, average, and poor readers. They will then undergo a battery of clinical screening tests involving visual, auditory, intellectual, and neuropsychological assessment to evaluate their overall status. The children will then take part in a series of experiments designed to measure the temporal development of local and global percepts in the visual system. Spatial and temporal filtering techniques will be applied to identify specific sensory mechanisms involved in the formation of such percepts. Additionally, the perceptual consequences of local and global processing characteristics on early visual operations such as perceptual grouping and figure-ground segregation will be investigated. A group of adult subjects will be included for comparability with previous studies using adult subjects, and to provide an index of developmental effects. An examination of the relations between local and global processing operations and early perceptual organization processes in normal and disabled readers may shed light on the underlying nature of any perceptual deficits that may contribute to reading difficulties. Comparisons between normal readers and adults will reveal developmental changes in local and global processing operations and their relation to early perceptual organization processes. Additionally, an analysis of the spatial and temporal response properties of the visual system that underlie local and global processing operations, and the perceptual functions that they mediate, may help to identify the underlying mechanisms responsible for perceptual deficits. Once identified, more effective intervention strategies can be devised.